Better main, refactoring of error system and Result type

Makefile

@@ -2,10 +2,11 @@ MAKEFLAGS="-j $(grep -c ^processor /proc/cpuinfo)"
 CXXFLAGS:=$(CXXFLAGS) -std=c++20 -Wall -Wextra -Werror=switch
 CPPFLAGS:=$(CPPFLAGS) -Ilib/expected/ -Ilib/ut/ -Isrc/
 
-Obj=bin/errors.o \
-		bin/lexer.o \
-		bin/parser.o \
-		bin/unicode.o \
+Obj=bin/errors.o        \
+		bin/lexer.o         \
+		bin/location.o      \
+		bin/parser.o        \
+		bin/unicode.o       \
 		bin/unicode_tables.o
 
 all: bin/musique bin/unit-tests

src/errors.cc

@@ -21,7 +21,7 @@ enum class Error_Level
 	Bug
 };
 
-static void error_heading(std::ostream &os, std::optional<Location> location, Error_Level lvl)
+static std::ostream& error_heading(std::ostream &os, std::optional<Location> location, Error_Level lvl)
 {
 	if (location) {
 		os << *location;
@@ -30,12 +30,34 @@ static void error_heading(std::ostream &os, std::optional<Location> location, Er
 	}
 
 	switch (lvl) {
-	case Error_Level::Bug:    os << ": implementation bug: "; return;
-	case Error_Level::Error:  os << ": error: ";              return;
-	case Error_Level::Notice: os << ": notice: ";             return;
+	case Error_Level::Error:  return os << ": error: ";
+	case Error_Level::Notice: return os << ": notice: ";
+
+	// This branch should be reached if we have Error_Level::Bug
+	// or definetely where error level is outside of enum Error_Level
+	default:                  return os << ": implementation bug: ";
 	}
 }
 
+void assert(bool condition, std::string message, Location loc)
+{
+	if (condition) return;
+	error_heading(std::cerr, loc, Error_Level::Bug) << message << std::endl;
+	std::exit(1);
+}
+
+[[noreturn]] void unimplemented(Location loc)
+{
+	error_heading(std::cerr, loc, Error_Level::Bug) << "this part was not implemented yet" << std::endl;
+	std::exit(1);
+}
+
+[[noreturn]] void unreachable(Location loc)
+{
+	error_heading(std::cerr, loc, Error_Level::Bug) << "this place should not be reached" << std::endl;
+	std::exit(1);
+}
+
 std::ostream& operator<<(std::ostream& os, Error const& err)
 {
 	error_heading(os, err.location, Error_Level::Error);

src/lexer.cc

@@ -221,7 +221,7 @@ auto Lexer::consume_if(auto first, auto second) -> bool
 
 void Lexer::rewind()
 {
-	assert(last_rune_length != 0);
+	assert(last_rune_length != 0, "cannot rewind to not existing rune");
 	source = { source.data() - last_rune_length, source.size() + last_rune_length };
 	token_length -= last_rune_length;
 	location = prev_location;
@@ -262,25 +262,5 @@ std::ostream& operator<<(std::ostream& os, Token::Type type)
 	case Token::Type::Operator:             return os << "OPERATOR";
 	case Token::Type::Expression_Separator: return os << "EXPRESSION SEPARATOR";
 	}
-
-	assert(false && "exhaustive handling of Token::Type enumeration");
-}
-
-Location Location::advance(u32 rune)
-{
-	switch (rune) {
-	case '\n':
-		line += 1;
-		[[fallthrough]];
-	case '\r':
-		column = 1;
-		return *this;
-	}
-	column += 1;
-	return *this;
-}
-
-std::ostream& operator<<(std::ostream& os, Location const& location)
-{
-	return os << location.filename << ':' << location.line << ':' << location.column;
+	unreachable();
 }

src/location.cc

@@ -0,0 +1,32 @@
+#include <musique.hh>
+
+Location Location::advance(u32 rune)
+{
+	switch (rune) {
+	case '\n':
+		line += 1;
+		[[fallthrough]];
+	case '\r':
+		column = 1;
+		return *this;
+	}
+	column += 1;
+	return *this;
+}
+
+std::ostream& operator<<(std::ostream& os, Location const& location)
+{
+	return os << location.filename << ':' << location.line << ':' << location.column;
+}
+
+#if defined(__cpp_lib_source_location)
+Location Location::caller(std::source_location loc = std::source_location::current())
+{
+	return Location { loc.file_name(), loc.line(), loc.column() };
+}
+#elif (__has_builtin(__builtin_FILE) and __has_builtin(__builtin_LINE))
+Location Location::caller(char const* file, usize line)
+{
+	return Location { file, line };
+}
+#endif

src/main.cc

@@ -1,7 +1,11 @@
 #include <iostream>
 #include <musique.hh>
 
+#include <filesystem>
 #include <span>
+#include <fstream>
+
+namespace fs = std::filesystem;
 
 static std::string_view pop(std::span<char const*> &span)
 {
@@ -10,11 +14,45 @@ static std::string_view pop(std::span<char const*> &span)
 	return element;
 }
 
-Result<Unit> Main(std::span<char const*> args)
+[[noreturn]]
+void usage()
 {
+	std::cerr <<
+		"usage: musique <options> [filename]\n"
+		"  where filename is path to file with Musique code that will be executed\n"
+		"  where options are:\n"
+		"    -c CODE\n"
+		"    --run CODE\n"
+		"      executes given code\n";
+	std::exit(1);
+}
+
+static Result<void> run(std::string_view source, std::string_view filename)
+{
+	Try(Parser::parse(source, filename));
+	std::cout << "successfully parsed: " << source << " \n";
+	return {};
+}
+
+// We make sure that through life of interpreter source code is allways allocated
+std::vector<std::string> eternal_sources;
+
+static Result<void> Main(std::span<char const*> args)
+{
+	if (args.empty()) {
+		usage();
+	}
+
+	std::vector<std::string_view> files;
+
 	while (not args.empty()) {
 		std::string_view arg = pop(args);
 
+		if (!arg.starts_with('-')) {
+			files.push_back(std::move(arg));
+			continue;
+		}
+
 		if (arg == "-c" || arg == "--run") {
 			if (args.empty()) {
 				std::cerr << "musique: error: option " << arg << " requires an argument" << std::endl;
@@ -22,8 +60,7 @@ Result<Unit> Main(std::span<char const*> args)
 			}
 
 			auto const source = pop(args);
-			Try(Parser::parse(source, "arguments"));
-			std::cout << "successfully parsed: " << source << " \n";
+			Try(run(source, "arguments"));
 			continue;
 		}
 
@@ -31,12 +68,27 @@ Result<Unit> Main(std::span<char const*> args)
 		std::exit(1);
 	}
 
+	for (auto const& path : files) {
+		if (not fs::exists(path)) {
+			std::cerr << "musique: error: couldn't open file: " << path << std::endl;
+			std::exit(1);
+		}
+
+		{
+			std::ifstream source_file{fs::path(path)};
+			eternal_sources.emplace_back(std::istreambuf_iterator<char>(source_file), std::istreambuf_iterator<char>());
+		}
+
+		Try(run(eternal_sources.back(), path));
+	}
+
 	return {};
 }
 
 int main(int argc, char const** argv)
 {
-	auto result = Main(std::span{ argv+1, usize(argc-1) });
+	auto const args = std::span(argv, argc).subspan(1);
+	auto const result = Main(args);
 	if (not result.has_value()) {
 		std::cerr << result.error() << std::flush;
 		return 1;

src/musique.hh

@@ -1,6 +1,5 @@
 #pragma once
 
-#include <cassert>
 #include <concepts>
 #include <cstdint>
 #include <cstring>
@@ -11,6 +10,15 @@
 #include <tl/expected.hpp>
 #include <variant>
 
+#if defined(__cpp_lib_source_location)
+#include <source_location>
+#endif
+
+// To make sure, that we don't collide with <cassert> macro
+#ifdef assert
+#undef assert
+#endif
+
 using u8  = std::uint8_t;
 using u16 = std::uint16_t;
 using u32 = std::uint32_t;
@@ -24,10 +32,6 @@ using i64 = std::int64_t;
 using usize = std::size_t;
 using isize = std::ptrdiff_t;
 
-struct Unit {};
-
-#define Fun(Function) ([]<typename ...T>(T&& ...args) { return (Function)(std::forward<T>(args)...); })
-
 // Error handling mechanism inspired by Andrew Kelly approach, that was implemented
 // as first class feature in Zig programming language.
 namespace errors
@@ -45,7 +49,7 @@ namespace errors
 struct Location
 {
 	std::string_view filename = "<unnamed>";
-	usize column = 1, line = 1;
+	usize line = 1, column = 1;
 
 	Location advance(u32 rune);
 
@@ -58,10 +62,27 @@ struct Location
 		loc.column = column;
 		return loc;
 	}
+
+	// Used to describe location of function call in interpreter (internal use only)
+#if defined(__cpp_lib_source_location)
+	static Location caller(std::source_location loc = std::source_location::current());
+#elif (__has_builtin(__builtin_FILE) and __has_builtin(__builtin_LINE))
+	static Location caller(char const* file = __builtin_FILE(), usize line = __builtin_LINE());
+#else
+#error Cannot implement Location::caller function
+#endif
 };
 
 std::ostream& operator<<(std::ostream& os, Location const& location);
 
+void assert(bool condition, std::string message, Location loc = Location::caller());
+
+// Marks part of code that was not implemented yet
+[[noreturn]] void unimplemented(Location loc = Location::caller());
+
+// Marks location that should not be reached
+[[noreturn]] void unreachable(Location loc = Location::caller());
+
 struct Error
 {
 	errors::Type type;
@@ -72,19 +93,29 @@ struct Error
 	Error with(Location) &&;
 };
 
+std::ostream& operator<<(std::ostream& os, Error const& err);
+
 template<typename T>
 struct Result : tl::expected<T, Error>
 {
 	using Storage = tl::expected<T, Error>;
 
-	constexpr Result()                         = default;
-	constexpr Result(Result const&)            = default;
-	constexpr Result(Result&&)                 = default;
-	constexpr Result& operator=(Result const&) = default;
-	constexpr Result& operator=(Result&&)      = default;
+	constexpr Result() = default;
+
+	template<typename ...Args> requires (not std::is_void_v<T>) && std::is_constructible_v<T, Args...>
+	constexpr Result(Args&& ...args)
+		: Storage( T{ std::forward<Args>(args)... } )
+	{
+	}
+
+	template<typename Arg> requires std::is_constructible_v<Storage, Arg>
+	constexpr Result(Arg &&arg)
+		: Storage(std::forward<Arg>(arg))
+	{
+	}
 
 	constexpr Result(errors::Type error)
-		: Storage(tl::unexpected(Error { error }))
+		: Storage(tl::unexpect, Error { error } )
 	{
 	}
 
@@ -93,36 +124,34 @@ struct Result : tl::expected<T, Error>
 	{
 	}
 
-	inline Result(tl::unexpected<Error> error)
-		: Storage(std::move(error))
-	{
-	}
-
-	template<typename ...Args>
-	requires std::is_constructible_v<T, Args...>
-	constexpr Result(Args&& ...args)
-		: Storage( T{ std::forward<Args>(args)... } )
+	// Internal function used for definition of Try macro
+	inline auto value() &&
 	{
+		if constexpr (not std::is_void_v<T>) {
+			return Storage::value();
+		}
 	}
 };
 
-std::ostream& operator<<(std::ostream& os, Error const& err);
-
 // NOTE This implementation requires C++ language extension: statement expressions
-// It's supported by GCC, other compilers i don't know
-#define Try(Value) ({ \
-	auto try_value = (Value); \
-	if (not try_value.has_value()) return tl::unexpected(try_value.error()); \
-	*std::move(try_value); \
+// It's supported by GCC and Clang, other compilers i don't know
+//
+// Inspired by SerenityOS TRY macro
+#define Try(Value)                               \
+	({                                             \
+		auto try_value = (Value);                    \
+		if (not try_value.has_value()) [[unlikely]]  \
+			return tl::unexpected(try_value.error());  \
+		std::move(try_value).value();                \
 	})
 
 namespace unicode
 {
 	inline namespace special_runes
 	{
-		constexpr u32 Rune_Error = 0xfffd;
-		constexpr u32 Rune_Self  = 0x80;
-		constexpr u32 Max_Bytes  = 4;
+		[[maybe_unused]] constexpr u32 Rune_Error = 0xfffd;
+		[[maybe_unused]] constexpr u32 Rune_Self  = 0x80;
+		[[maybe_unused]] constexpr u32 Max_Bytes  = 4;
 	}
 
 	// is_digit returns true if `digit` is ASCII digit
@@ -257,9 +286,6 @@ struct Ast
 	Token token;
 };
 
-template<typename Expected, typename ...T>
-concept Var_Args = (std::is_same_v<Expected, T> && ...) && (sizeof...(T) >= 1);
-
 struct Parser
 {
 	std::vector<Token> tokens;
@@ -280,7 +306,7 @@ struct Parser
 
 	// Ensures that current token has one of types given.
 	// Otherwise returns error
-	Result<Unit> ensure(Token::Type type) const;
+	Result<void> ensure(Token::Type type) const;
 };
 
 namespace errors

src/parser.cc

@@ -49,13 +49,13 @@ bool Parser::expect(Token::Type type) const
 	return token_id < tokens.size() && tokens[token_id].type == type;
 }
 
-Result<Unit> Parser::ensure(Token::Type type) const
+Result<void> Parser::ensure(Token::Type type) const
 {
 	return token_id >= tokens.size()
 		? errors::unexpected_end_of_source(tokens.back().location)
 		: tokens[token_id].type != type
 		? errors::unexpected_token(type, tokens[token_id])
-		: Result<Unit>{};
+		: Result<void>{};
 }
 
 Ast Ast::literal(Token token)